Wireless high-date rate communications

ABSTRACT

A base station apparatus is provided. The base station apparatus includes an orthogonal frequency division multiplexed (OFDM) encoder and a time division multiplexer. The OFDM encoder is configured to encode a plurality of data streams into a corresponding plurality of OFDM tones, where one of the corresponding plurality of OFDM tones includes an OFDM preamble tone that indicates a mapping of remaining OFDM tones within the plurality of OFDM tones to one or more of a plurality of mobile stations, and indicates at least one of the plurality of tones addressed to a particular mobile device, and wherein the preamble tone is not fixed to the selected particular mobile device through communication. multiplexes a plurality of streams over a forward link channel for receipt by the plurality of mobile stations, where the corresponding plurality of OFDM tones are encoded as one of the plurality of streams.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the following U.S. ProvisionalApplications, each of which is herein incorporated by reference for allintents and purposes.

FILING SERIAL NUMBER DATE TITLE 61118484 Nov. 28, 2008 WIRELESSHIGH-DATE (VTU.09-0005-US) RATE COMMUNICATIONS 61118485 Nov. 28, 2008OFDMA SUBBAND INTER- (VTU.09-0006-US) FERENCE MANAGEMENT AND MULTIUSERMULTIPLEXING

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to the field of cellularcommunications, and more particularly to a method and apparatus forimproving the communications throughput over a cellular network.

2. Description of the Related Art

The cell phone industry is undergoing exponential growth, not only inthe this country, but all over the world. In fact, it is well known thatthe over twenty percent of the adult population in the United States donot even have a traditional landline telephone. In addition to those whodo not own a conventional telephone, nearly ninety percent of the adultpopulation owns a wireless phone.

And the usage of cell phones is increasing as well over the use oftraditional landline telephone coverage. In fact, one in seven adultsnow uses only cell phones. Whereas in the past cell phones were usedwhen a landline was not available or under emergency conditions, lowercarrier rates, affordability of family packages, and freemobile-to-mobile or friend-to-friend promotions have fostered insignificant increases in usage. It is not uncommon today to walk intoany public forum or facility and notice a majority of the people theretalking on their cell phones.

The ability to communicate using a mobile phone, or mobile station, hasbeen available since the middle of the last century. However, during the1990's so-called “2G” or second generation mobile phone systems wereprovided that began the growth in both deployment and usage that wecurrently enjoy today. These initial systems predominately provided forthe routing and reliable servicing of voice calls between parties. And,as one skilled in the art will appreciate, there are a number of timingand latency requirements associated with transmission and reception ofvoice data in order to maintain quality of service.

And although wireless cellular network technologies have continued toprovide improvements related to the ability to process voice calls,there has also been an enormous pull on the industry to provideimprovements related to the processing of data as well as voice. It isnot uncommon today to find many cell phone users who not only placevoice calls over a cellular network, but who also check their email,send text messages, and browse the internet.

Accordingly, a number of technologies are under development to improvethe quality and throughput of data. These so-called “3G” or thirdgeneration cellular communications technologies are highly optimized forthe reliable transfer of packet data instead of voice data. Hence, 3Gdata protocols such as EDGE® and EV-DO technologies are not generallycharacterized modulation techniques, but more so by performance metrics(e.g., 5 Megabits per second throughput). And this is because although agiven data connection must be guaranteed some minimal level of latencyand throughput, the timing required to transfer data such as a textmessage pales in comparison to that required to transfer voiceinformation.

However, as one skilled in the art will appreciate, there are othermeans for processing voice calls that over a conventional cellular voicenetwork. For example, voice over internet protocol (VOIP) has been usedfor many years as one way of taking advantage of the throughputcapabilities of a high speed data network in order to send and receivevoice information. And while cellular providers are certainly embracingVOIP to increase their network's ability to process a greater number ofvoice calls, the present inventors have noted that when a data networksuch as EV-DO is utilized in part to process VOIP calls, the throughputpotential of that network significantly decreases due to the timingconstraints associated with the processing of voice. More specifically,to maintain quality of service, voice information must be transmittedregularly and frequently, typically every 20 milliseconds. And when apacketized data network such as an EV-DO network is employed to transmitVOIP data, because EV-DO is a time division multiplexed deliveryprotocol, the timing requirements of VOIP dictate that regular timeslots be allocated and reserved for the data associated with a VOIPcall—regardless of the amount of voice data that is to be transmitted,which is most often a small amount of data relative to the datanetwork's throughput ability.

Consequently, the present inventors have noted the inefficienciesassociated with the utilization of data networks such as EV-DO toprocess VOIP data in addition to other types of data. They have observedsignificant decreases in these data networks throughput rates as afunction of the number of VOIP calls which are processed.

Accordingly, what is needed is a technique that enables a cellular datanetwork to process increasing numbers of VOIP calls that does notnotably affect the network's throughput rate.

In addition, what is needed is an apparatus and method for interlacingVOIP data and other forms of data within an existing data protocol inorder to maximize the data transfer rate.

What is also needed is a mechanism for processing VOIP calls over a datanetwork that leverages unused bandwidth of an existing data network, butwhich also compatible with legacy cellular devices.

SUMMARY OF THE INVENTION

The present invention, among other applications, is directed to solvingthe above-noted problems and addresses other problems, disadvantages,and limitations of the prior art.

The present invention provides a superior technique for increasing thethroughput of a cellular data network, particularly when that network isbeing employed to service VIOP calls. In one embodiment, a base stationwirelessly coupled to a plurality of mobile devices, comprising a dataencoder and a time division multiplexer. The data encoder is configuredto receive a preamble signal and a plurality of data streams, which areencoded into a corresponding preamble tone and a corresponding pluralityof tones, wherein the preamble tone indicates a mapping of the pluralityof tones in response to one or more of the plurality of mobile devices,and wherein the preamble tone indicates at least one of the plurality oftones which are addressed to a particular mobile device, and wherein thepreamble tone is not fixed to the selected particular mobile devicethrough communication. The time division multiplexer is coupled to saiddata encoder, configured to multiplex the preamble tone and theplurality of tones in timely fashion for receipt by the plurality ofmobile devices.

One aspect of the present invention contemplates a method for a basestation wirelessly coupled to a plurality of mobile devices, comprisingreceiving and encoding a preamble signal and a plurality of data streamsinto a corresponding preamble tone and a corresponding plurality oftones, wherein the preamble tone indicates a mapping of the plurality oftones in response to one or more of the plurality of mobile devices, andwherein the preamble tone indicates at least one of the plurality oftones which are addressed to a particular mobile device, and wherein thepreamble tone is not fixed to the selected particular mobile devicethrough communication; and multiplexing the preamble tone and theplurality of tones in timely fashion for receipt by the plurality ofmobile devices.

One aspect of the present invention comprehends a mobile devicewirelessly coupled to a plurality of base stations, comprising adecoder, a preamble decoder and a processor. The decoder, configured todemultiplex and decode a plurality of tones received from at least oneof the plurality of base stations. The preamble decoder, configured todecode a preamble tone received from at least one of the plurality ofbase stations, wherein the decoded preamble tone indicates one or moreof the plurality of tones are transmitted for the mobile device, andwherein the preamble tone is not fixed to the mobile device throughcommunication. And the processor, coupled to said decoder and saidpreamble decoder, configured to process one or more of the plurality oftones indicated by the decoded preamble tone, and send a data ratecontrol signal of the corresponding base station.

One aspect of the present invention comprehends a method for a mobiledevice wirelessly coupled to a plurality of base stations, comprisingdemultiplexing and decoding a plurality of tones received from one ofthe plurality of base stations; decoding a preamble tone received fromone of the plurality of base stations, wherein the decoded preamble toneindicates one or more of the plurality of tones are transmitted for themobile device, and wherein the preamble tone is not fixed to the mobiledevice through communication; processing one or more of the plurality oftones indicated by the decoded preamble tone; and sending a data ratecontrol signal of the corresponding base station.

Another aspect of the present invention comprehends a system comprisinga plurality of base station and a plurality of mobile device. Each ofthe plurality of base station, further comprising a data encoder, and atime division multiplexer. The data encoder, configured to receive apreamble signal and a plurality of data streams, which are encoded intoa corresponding preamble tone and a corresponding plurality of tones,wherein the preamble tone indicates a mapping of the plurality of tonesin response to one or more of the plurality of mobile devices, andwherein the preamble tone indicates at least one of the plurality oftones which are addressed to a particular mobile device, and thepreamble tone is not fixed to the selected particular mobile devicethrough communication. The time division multiplexer, coupled to saiddata encoder, configured to multiplex the preamble tone and theplurality of tones in timely fashion for receipt by the plurality ofmobile devices. Each of the plurality of mobile device, wirelesslycouple to one or more of the plurality of base stations, furthercomprising a decoder, a preamble decoder, and a processor. The decoder,configured to demultiplex and decode the plurality of tones receivedfrom at least one of the plurality of base stations. The preambledecoder, configured to decode the preamble tone received from at leastone of the plurality of base stations, wherein the decoded preamble toneindicates one or more of the plurality of tones are transmitted for themobile device; and The processor, coupled to said decoder and saidpreamble decoder, configured to process one or more of the plurality oftones indicated by the decoded preamble tone, and send a data ratecontrol signal of the corresponding base station.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features, and advantages of the presentinvention will become better understood with regard to the followingdescription, and accompanying drawings where:

FIG. 1 is a block diagram illustrating an exemplary scenario within acellular network where a number of base stations are communicating withnumerous mobile stations;

FIG. 2 is a diagram depicting a present data evolution data-optimized(EV-DO) forward link frame which is employed to transfer the datatraffic in the example of FIG. 1;

FIG. 3 is a block diagram featuring an EV-DO forward link multi-userframe according to one embodiment of the present invention;

FIG. 4 is a block diagram showing a multi-user base station mechanismaccording to one embodiment of the present invention;

FIG. 5 is a block diagram illustrating a multi-user mobile stationmechanism according to one embodiment of the present invention;

FIG. 6 is a block diagram detailing a base station mechanism accordingto the one embodiment of present invention for managing sub-bandinterference; and

FIG. 7 is a block diagram showing data sub-frames corresponding to threebase stations according to one embodiment of the present invention whenthe base stations are communicating with mobile stations in a sub-bandinterference reduction mode.

DETAILED DESCRIPTION

The following description is presented to enable one of ordinary skillin the art to make and use the present invention as provided within thecontext of a particular application and its requirements. Variousmodifications to the preferred embodiment will, however, be apparent toone skilled in the art, and the general principles defined herein may beapplied to other embodiments. Therefore, the present invention is notintended to be limited to the particular embodiments shown and describedherein, but is to be accorded the widest scope consistent with theprinciples and novel features herein disclosed.

In view of the above background on wireless voice and data networks andassociated techniques employed within present day wireless networks forthe transfer of data, including voice over internet protocol (VOIP), adiscussion of the throughput inefficiencies associated with thesetechniques invention will now be presented with reference to FIGS. 1-2.Following this, a discussion of the present invention will be providedwith reference to FIGS. 3-7. The present invention overcomes the notedthroughput limitations associated with present day wireless datatransfer mechanisms by providing techniques whereby more data can bedelivered to multiple users over existing wireless links. In addition,the present invention provides features that allow for betterinterference management between adjacent cells. And the mechanismsaccording to the present invention are fully backwards compatible withexisting legacy protocols.

Referring now to FIG. 1, a block diagram 100 is presented illustratingan exemplary scenario within a cellular network where a number of basestations 101 are communicating with numerous mobile stations 103 for athree cellular applications, that is voice, data, and voice overinternet protocol (VOIP). The block diagram 100 shows three cellularbase stations 101 that each provide for wireless radio communicationswith one or more mobile stations 103 within their respective areas ofcoverage 102, also known as cells 102.

Cellular signals are received from and transmitted to a given mobilestation 103 by a particular base station 101 when the mobile station 103is within a cell 102 corresponding to the base station 101, and when thegiven base station 101 has been assigned to provide for communicationswith the mobile station 103 by a base station controller (not shown).Accordingly, the strength of the respective transmitted and receivedsignals generally seen by both the mobile station 103 and the given basestation 101 is a function of the location of the mobile station 103 atit traverses through a particular cell 102. The number of base stations101 shown in the diagram, and their respective cells 102, along with thenumber of mobile stations 103, is presented for illustrative purposesonly. As one skilled in the art will appreciate, the number of cells 102within which a particular mobile station 103 falls is a function of themobile station's location and the deployment pattern of the basestations 101.

Generally, there is significant overlap of adjacent cells 102 to providefor reliable handoff of a mobile station 103 from one base station 101to an adjacent base station 101 as the mobile station 103 traverses thecells 102.

The block diagram 100 depicts mobile stations 103 that are employingthree modes of cellular communications areas as they send/receivesignals to/from the base stations 101. That is, some of the mobilesstations 103 are employing the cellular network to send and receivevoice signals, which is conventional voice communications such as a callfrom one mobile station 101 to either another mobile station 101 or to atelephone over the public switched telephone network (not shown). Othermobile stations 103 are employing the cellular network to transfer datasuch as email, text messages, and the like. And yet other mobilestations 103 are employing the cellular network to transmit and receivedata related to VOIP communications. Presently, the SKYPE® applicationis widely used for VOIP communications although other applications areavailable to provide for VOIP. In addition, cellular telecommunicationcompanies are strongly considering the use of VOIP under conditionswhere conventional voice communication channels are not available or areless desirable over a data communication channel. Thus, technologies arecurrently being developed which allow for the seamless handover of acall between a voice channel and a data channel within a given cellularnetwork.

There are several extant network types and protocols presently deployedwhich successfully accomplish the voice communication function notedabove such as Global System for Mobile Communications (GSM), whichutilizes frequency division multiple access (FDMA) as its principalaccess technology, and IS-95 (also known as CDMA2000), which utilizescode division multiple access (CDMA) as its principal access scheme. GSMis a somewhat older technology but is prevalently deployed today.CDMA2000 is a newer, more robust access scheme, which is growing interms of deployment and market share because of its increased usercapacity, more reliable signaling techniques, and because it allows forsignificant growth in the concurrent transmission of packetized data inaddition to voice communications.

Likewise, several existing network types and protocols provide for thetransfer of data signals, as understood by one of ordinary skill in theart, some application and service, for example the VoIP service areincluded in data communications, and since data communications aretraditionally packet-based schemes, the same protocol within a cellularnetwork is generally used to transfer both kinds of information. Onesuch standard for transmission of data and VOIP signals is thewell-known Evolution-Data Optimized (EV-DO) standard, which is alsoknown as Evolution-Data Only. The EV-DO standard defines the protocolsthat support the transmission of data as described above over a wirelessradio network. EV-DO uses multiplexing techniques including CDMA as wellas time division multiple access (TDMA) to maximize both individualuser's throughput and the overall system throughput. Because EV-DOemploys CDMA, it pairs well as the data transfer protocol withinnetworks that utilize CDMA2000 as the protocol for voice communicationsbecause of the ability to utilize common hardware within base stations101 and mobile stations 103 to perform both forms (i.e., voice anddata/VOIP) of cellular communications.

EV-DO is in face a variant of CDMA2000 that is oriented towardsupporting very high data transfer rates and thus is considered a “3G”protocol by those skilled in the art. An EV-DO channel has a bandwidthof 1.25 MHz, which is the same size of a CDMA2000 channel. And EV-DOemploys a similar code division encoding scheme as does CDMA200 channelsfor voice communications. But the specific EV-DO channel structure, isentirely difference than a CDMA2000 voice channel because the type ofdata that is transferred over an EV-DO channel is packet-based, and isthus not subject to timing and latency requirements that are mandatoryfor voice communications over a circuit switched network. In otherwords, for voice communications, it is generally required to maintainquality of service that voice information be transferred roughly every20 milliseconds between a mobile station 103 and a base station 101. Butthere is typically no critical latency requirement related to thetransfer of, say, an email message.

Consequently, EV-DO standards provide for a number of different transferrates from a base station 101 to a mobile station 101 which are basedupon the mobile station's ability to reliably receive the data.

Currently, EV-DO networks provide for downlink (or, “forward link”)transfers of data to a mobile device 103 up to almost 5 Megabits persecond (Mb/s). Uplink (or “reverse link”) speeds are much slower.

The primary difference between an EV-DO channel and a CDMA2000 channelis that the EV-DO channel employs time division multiple access (TDMA)techniques to provide data to one or more mobile stations 103 on thesame forward link. In contrast to a CDMA2000 voice channel, a mobilestation 103 that is communicating over an EV-DO channel has full use ofthe forward link within a particular cell 102 during a given timeperiod, or “slot.” Consequently, a base station 101 that provides forEV-DO is able to employ different modulation schemes for differentusers, according to the users' ability to receive data. Thus, mobilestations 103 that are in very strong signal reception conditions areserved by the base station 101 with very complex modulation techniquesthat support high transfer rates, while those mobile stations 103 thatare in very poor signal reception conditions are served with lesscomplex and more reliable modulation schemes. And the assignment ofslots to the mobile stations 103 within a given cell 102 is alsodetermined by a mobile station's ability to receive, that is, thosemobile stations 103 that are capable of reliably receiving data arefavored by the protocol, thus efficiently utilizing network resourceswhile still providing for data transfer to those mobile stations 103that can only support low transfer rates.

The ability of EV-DO to tailor data transfer rates to suit more capablemobile stations 103 notwithstanding, the use of VOIP as a means forenhancing a cellular network's ability to process a great number ofvoice calls has been noted by the present inventors. More specifically,the present inventors have observed several limitations of existingEV-DO technologies when the number of VOIP transactions is increased inwithin a given cellular coverage area 102. These observations are betterunderstood and will now be discussed with reference to FIG. 2.

Turning to FIG. 2, a diagram 200 is presented depicting a present datapacket forward link frame 201 (or “packet” 201) which is employed totransfer the data and VoIP traffic in the example of FIG. 1. The frame201 includes 16 slots 202, which are time division multiplexed over anCDMA channel to provide for the transmission of data packet. An slot 202is 1.667 milliseconds in duration, corresponding to 2048 chips of a1.2288 Megahertz CDMA carrier signal.

Each of the slots 202 comprises sub-frame fields 204-206 that includetwo pilot sub-frame fields 206, four media access channel (MAC)sub-frame fields 205, and four data sub-frame fields 204. The pilotsub-frames 206 are provided to enable the mobile station to find andidentify the CDMA channel. The MAC sub-frames 205 are provided toindicate to the mobile station when and where their respective datatraffic is located in the stream. And the data sub-frames 204 comprisethe actually data that is being transferred to the mobile station. Asone skilled in the art will appreciate, other channels are periodicallyinterlaced into the stream, but the diagram 200 shown is sufficient toteach the limitations of existing technologies along with the presentinvention.

In operation, one or more slots 202 are assigned to mobile stationswithin a given cell based upon each of the mobile station's ability toreceive data over the channel. In fact, the mobile stations each measurethe signal strength of the channel and they each estimate a sustainabledata rate that can be received. This information is transmitted back tothe base station servicing the cell over a digital rate control (DRC)channel. Accordingly, if a given cell phone is able to sustain a maximumdata rate, then scheduling logic within the base station assigns moreslots 202 for the transfer, and the modulation scheme for each of theslots 202 is selected to comport with the maximum data rate. Poorreceivers are guaranteed a minimum transfer rate.

All mobile stations receive and decode all of the frames 201 that aretransmitted, and the information within each of the MAC sub-frames 205indicate whether a corresponding data sub-frame 204 is intended for aparticular mobile station or not. It is important to understand thatalthough many slots 202 within a particular frame 201 may be addressedto a single mobile station, the data sub-frames 204 within each slot 202are intended only for the single mobile station. In other words, thedata sub-frames 204 within a particular slot 202 contain information forthe single mobile station, regardless of the quantity of informationthat is passed over the channel.

A present day forward link supports a number of different modulationschemes to provide for a wide range of receive capabilities for mobilestations within a given sector. And for the transfer of data only,because there are no latency requirements, the existing protocol, suchas EV-DO, is indeed effective and bandwidth efficient. However, whenVOIP applications are introduced into the mix of data that is beingtransmitted over an EV-DO channel, timing and latency requirements getadded to the factors that a base station must employ to schedule theslots 202 within the EV-DO frames 201 that are transmitted.

Accordingly, it is common practice in the art for a base station to setaside, or reserve periodic slots 202 to support VOIP service becausesome form of information must be transmitted roughly every 20milliseconds regardless of whether a corresponding VOIP call is activeor idle. And the present inventors have noted that VOIP information issignificantly idle, or absent, relative to the frame rate of a givenCDMA channel. That is, digitized and packetized voice information iseffectively transmitted in bursts because such is the nature of voicecommunications.

Yet, it is never known to the base station when these bursts will occur,so periodic slots 202, say one slot per frame, must be reserved tosupport VOIP, regardless of the information content therein. And thepresent inventors have observed that reserving periodic slots 202 tosupport a VOIP call within an CDMA channel is very bandwidth inefficientand further limits the throughput of the channel. If one considersreserving one slot 202 within each successive frame 201 to support agiven VOIP call, then it follows that 16 VOIP calls will entirelysaturate a given channel, and such a scenario does not take intoconsideration the network load related to data communications within thecell.

Heretofore, the limitations and disadvantages associated with VOIPcommunications via EV-DO have been tolerable because of the relativelylow use of this communications technique. But as the use of VOIPtechniques increase, it is anticipated that current EV-DO mechanismswill cease to provide the throughput that will be required.

Accordingly, the present inventors have developed apparatus and methodsto expand the capabilities of existing system mechanisms to supporthigher throughput rates at a slot level. And these apparatus and methodsare entirely compatible with existing EV-DO mechanisms. The presentinvention provides for encoding a number of sub-channels supportingmultiple mobile stations within a single slot so that the resourceswithin the single slot for transmitting data are employed moreefficiently. The present invention utilized orthogonal frequencydivision multiplexing (OFDM) techniques to encode up to 16 sub-channelswithin a single slot 202, thereby allowing unused resources which wouldbe otherwise reserved for use by a single mobile station to be employedmore efficiently, thus increasing the throughput of the network. Thepresent invention will now be described with reference to FIGS. 3-7.

Referring to FIG. 3, according to one embodiment in the presentinvention, a block diagram 300 is depicted featuring an forward linkmulti-user frame 301. Like the forward link frame 201 of FIG. 2, themulti-user frame 301 of FIG. 3 includes 16 slots 302, which are timedivision multiplexed over an CDMA channel. It could be understood by oneof the skilled in the art, the frame structure in EV-DO system ispresented for illustration.

Each of the slots 302 comprises sub-frame fields 304-306 that includetwo pilot sub-frame fields 306, four media access channel (MAC)sub-frame fields 305, and four data sub-frame fields 304. The pilotsub-frames 306 are provided to enable the mobile stations to find andidentify the CDMA channel. The MAC sub-frames 305 are provided toindicate to the mobile stations when and where their respective datatraffic is located in the stream. And the data sub-frames 304 comprisethe actually data that is being transferred to the mobile stations.

In contrast to an existing MAC sub-frame 205, a MAC sub-frame 305according to the present invention contemplates one or more values thatindicate data in a corresponding data sub-frame 304 is “shared,” thatis, the information therein is intended for more than a single mobilestation. The one or more values are taken from those spare values withina given network and only those mobile stations that are deployedaccording to the present invention will recognize such data to beshared. Legacy mobile stations will simple decode the MAC sub-field 305and determine that the corresponding data sub-field 304 is for anothermobile station.

In operation, one or more slots 302 are assigned to mobile stationswithin a given cell based upon each of the mobile station's ability toreceive data over the channel. And in keeping with the base stations,the mobile stations each measure the signal strength of the channel andthey each estimate a sustainable data rate that can be received. Thisinformation is transmitted back to the base station servicing the cellover a data rate control (DRC) channel. Accordingly, if a given cellphone is able to sustain a maximum data rate, then scheduling logicwithin the base station assigns more slots 302 for the transfer, and themodulation scheme for each of the slots 302 is selected to comport withthe maximum data rate. In addition, when a cell phone enters aparticular cell, a base station according to the present inventiondetermines whether or not the particular cell is capable of supportingmulti-user frames 301.

All mobile stations within the cell receive and decode all of the frames301 that are transmitted and, in contrast to present day EV-DOstrategies, one or more of the data sub-fields 304 within a slot 302 maycomprise a plurality of sub-frame channels 307 which are OFDM encodedand one or more of the plurality of sub-frame channels 307 may bedesignated for a single user (i.e., a single mobile station) or the oneor more sub-frame channels 307 may be mapped to different users. TheOFDM sub-frame channels are also known as “tones”.

In one embodiment, the tones within a given data sub-frame 304 aregenerated via modulating the data to be transmitted via a correspondingnumber of closely-spaced orthogonal sub-carriers and then the tones aresummed together prior to CDMA encoding. It is beyond the scope of thepresent application to provide an in-depth tutorial of the techniquesassociated with OFDM. It is sufficient to note that OFDM tones asdescribed herein can be effectively employed within a single datasub-frame 304 according to the present invention to provide formulti-user delivery of data within a single EV-DO slot 302.

In addition, one particular OFDM tone 306 is dedicated according to thepresent invention as a preamble tone 306 for the corresponding datasub-frame 304. That is, the preamble tone 306 includes similarinformation within the MAC sub-frame 305, that indicates a mapping ofthe remaining OFDM tones 307 to one or more of a plurality of mobilestations according to the present invention. Accordingly, when a mobilestation according to the present invention decodes a MAC sub-frame 305that indicate a corresponding data sub-frame 304 contains shared OFDMtones 307, then the mobile station will decode the preamble tone 306 todetermine which of the remaining tones 307 within the data sub-frame 304contain information that is addressed to the mobile station. Tones 307which are addressed to the mobile station, as indicated by the preambletone, are processed accordingly. Tones 307 which are not addressed tothe mobile station are thus discarded.

Consequently, an packet 301 according to the present invention iscapable of providing for increased throughput over an forward linkchannel. This is particularly relevant during scenarios wherein a numberof the mobile stations within a given cell or network of cells areutilizing the network for VOIP applications. Thus, during significantportions of a VOIP call when very little data is transmitted, only aportion of the resources associated with a given, reserved slot 302 areemployed in association with the call. In one embodiment, only a singletone 307 may be employed to support the call. And the remaining tones307 can be utilized by the network for transmission of data, or fortransmission of information corresponding to other VOIP calls.

In one embodiment, 16 OFDM tones 307 are generated for a given slot 302,where a first tone 306 is designated at the preamble tone 306.

It should be noticed that the order or pattern of OFDM tone 1-15 is notfixed through the transmission. In one embodiment, the order or patternchanges from one quarter slot to the next one quarter slot, or from onesymbol to the next symbol. That is when “hopping” occurs. Ascomprehended by the ordinary people, “hopping” is out of the scope ofthe present invention. But it should be known that the hopping scheme ispredefined for each mobile and base station, and also a function of basestation ID, mobile ID, sector ID, etc. Meanwhile, different hoppingscheme did not affect the above structure and/or mapping in one of theslots.

Now turning to FIG. 4, a block diagram is presented showing a multi-userbase station mechanism 400 according to the present invention. The basestation 400 includes a data encoder 401 that receives a plurality ofdata streams D16:D1 along with a preamble stream PRE provided by apreamble generator 406. The data encoder 401 is coupled to an OFDMencoder 402 via a corresponding plurality of encoded data busses E15:E1along with an encoded preamble bus EPRE. The OFDM encoder 402 is coupledto summation logic 403 via a corresponding number of OFDM tone bussesO15:O1 along with an OFDM preamble tone bus OPRE. The summation logic403 is coupled to a modulator 404, which also receives a Walsh code. Theoutput of the modulator 404 is coupled to one input of a time divisionmultiplexer (TDM) 405. The remaining inputs of the TDM 405 receive Walshencoded signals from other data corresponding to the remain sub-frame.TDM 405 generates a forward link data output EV-DO FL, which is routedto a transmitter (not shown) within the base station 400 fortransmission to mobile stations within a corresponding cellular coveragearea.

In operation, data streams (e.g., data or VOIP) D15:D1 according to thepresent invention are routed to the data encoder 401, which provides forencoding of the information according to scheduling prioritiesdetermined by the base station 400. For example, in one embodiment, someof the data streams D15:D1 may be empty, that is null sequences, orsequences void of information. In another embodiment, the data streamsD15:D1 may be associated with a corresponding number of mobile stations,that is, 15 streams D15:D1 for each of 15 mobile stations. In anotherembodiment, a first subset of the data streams D15:D1 correspond toinformation associated with a single mobile station. The preamblegenerator 406 provides information over bus PRE that indicates a mappingof data stream D15:D1 to mobile station.

The encoded data E15:E1 and preamble EPRE are routed to the OFDM encoder402, which generates the corresponding plurality of OFDM tones O15:O1along with the preamble tone OPRE according to known OFDM modulationmethods. The OFDM tones O15:O1 and preamble OPRE are summed together bythe summing logic 403 to produce a composite tone which is modulated byone of a plurality of Walsh codes by the modulator 404. The output ofthe modulator 404, W15, is routed along with a remaining number of Walshmodulated streams W14:W0 to the TDM 405, which generates the EV-DO FLstream in accordance with scheduling parameters determined by the basestation 400. It is noted that the TDM 405 does not multiplex each of theWalsh streams W15:W0 in successively or in equal slot times, but rathergenerates an EV-DO forward link slot stream where one of the Walshstreams W15:W0 is provided in a given EV-DO FL slot. For example,scheduling priorities may determine that a subset of the Walsh streamsW15:W0 be allocated slots during a following number of EV-DO packets andthus the TDM provides the EV-DO FL stream accordingly. In oneembodiment, the OFDM encoded Walsh stream W15 is multiplexed by the TDM405 into one or more EV-DO slots.

In one embodiment, there are 15 data streams D15:D1 produce acorresponding number of OFDM tones O15:O1 along with a preamble toneOPRE indicating a mapping of tones O15:O1 to mobile station. Othernumbers of tones are additionally contemplated such as 8 tones 32 tones,and 64 tones.

Turning now to FIG. 5, a block diagram is presented illustrating amulti-user mobile station mechanism 500 according to the presentinvention. The mobile station 500 includes a demultiplexer/decoder 501that receives a multi-user EV-DO forward link stream as generated andtransmitted by the base station 400 of FIG. 4. The demultiplexer/decoder501 outputs one of a plurality of slot streams RO that have beengenerated by the base station 400 and which is designated as a sharedslot stream by a corresponding MAC sub-frame field. Accordingly, slotstream RO may be generated in an existing EV-DO configuration atintervals described above with reference to FIG. 3.

The shared slot stream RO is coupled to an OFDM decoder, which decodesthe additive stream RO into a plurality of OFDM tone streams D15:D1 anda corresponding OFDM preamble tone stream DPRE. The preamble tone streamDPRE is coupled to a preamble decoder 504. The remaining tone streamsD15:D1 are coupled to a data decoder 503. The preamble decoder, inaccordance with the information encoded in the preamble tone DPRE,indicates on a select bus SEL[15:1] which of the tone streams D15:D1 areaddressed to the particular mobile station 500. Those streams D15:D1which are addressed to the mobile station 500 are decoded by the datadecoder and subsequently sent to data processing logic (not shown)within the mobile station. Those streams D15:D1 which are not addressedto the mobile station 500 are discarded.

Accordingly, low data rate information, such as VOIP data, can be OFDMmultiplexed along with other data within a single EV-DO packet accordingto the present invention, thus increasing the throughput of a CDMAchannel and providing the capability to serve more VOIP users over thatwhich has heretofore been provided. In addition, the present inventionallows for compatibility with legacy users as well.

In addition to the above-noted features and advantages, the presentinvention provides a very useful technique for managing sub-bandinterference. That is, in the scenario where adjacent base stations aretransmitting CDMA channels on adjacent channel frequencies, conditionsmay exist where one or more mobile stations within a given basestation's cell are operating under less than desirable receptionconditions because of interference resulting from an adjacent basestation's transmissions. One such example is when a mobile station is onthe fringe or intersection of two adjacent cells served by base stationstransmitting in adjacent frequency bands.

The present invention overcomes the above limitation, and more, byproviding a mechanism whereby particular subsets of OFDM tones, asdescribed above, are exclusively allocated to adjacent base stations fortransmission in a multi-user EV-DO packet slot for those mobile stationsexhibiting weak reception.

Turning now to FIG. 6, a block diagram is presented detailing a basestation mechanism 600 according to the present invention for managingsub-band interference. The base station 600 includes sub-bandinterference logic 601 that receives a plurality of DRC channelsDRCN:DRC0 from a corresponding number of mobile stations which have beenassigned to the base station 600 by a base station controller (notshown). Based upon the values of the DRC channels DRCN:DRC0, thesub-band interference logic 601 determines whether the mobile stationsfall into either a strong traffic category or a weak traffic category bycomparing with a threshold, which will be illustrated later. Indicationsof these stations are provided to a weak traffic manager 602 via weaktraffic bus WEAK and to a strong traffic manage 603 via a strong trafficbus STRONG. Traffic (e.g., data and/or VOIP streams) corresponding toeach of the mobile stations is provided to both the strong trafficmanager 603 and the weak traffic manager 602 via a traffic busTRAFFIC[N:0]. A sub-band interference registry 604 is also coupled tothe weak traffic manager 602. The weak traffic manager 602 generatesOFDM tones corresponding to the weak traffic on bus WEAKTRAFFIC and thestrong traffic manager 603 generates OFDM tones corresponding to thestrong traffic on bus STRONGTRAFFIC.

In operation, if the DRC value of a given mobile station is below athreshold, as determined by configuration, so as to be designated as aweak user, the sub-band interference logic 601 indicates this case tothe weak traffic manager 602 via bus WEAK. The weak traffic manager 602subsequently generates OFDM tones for the weak user. If the DRC value ofthe given mobile station is above the threshold so as to be designatedas a strong user, the sub-band interference logic 601 indicates thiscase to the strong traffic manager 603 via bus STRONG. The strongtraffic manager 603 subsequently generates OFDM tones for the stronguser.

Traffic for strong users employs all of the OFDM tones provided for by agiven configuration, for example, as described above with reference toFIGS. 3-5. However, traffic for weak users is generated on a designatedsubset of the OFDM tones provided for by the given configuration, whereadjacent base stations 600 employ exclusively different subsets of theavailable OFDM tones. Typically, the subset of tones available for aparticular base station 600 are stored in the sub-band interferenceregistry 604 and are only used to generate the weak traffic stream. Thisapproach to sub-band interference management is more particularlyillustrated with in FIG. 7.

FIG. 7 is a block diagram 700 showing EV-DO data sub-frames 701, 704,707 corresponding the three base stations according to the presentinvention when the base stations are communicating with mobile stationsin a sub-band interference reduction mode. Each of the data sub-frames701, 704, 707 has a plurality of OFDM tones 702, 705, 708 along with apreamble tone 703, 706, 709 that maps the associated OFDM tones 702,705, 708 to one or more mobile stations within the base station'srespective cells.

To preclude interference in adjacent cells, weak traffic signals asdescribed above with reference to FIG. 6 are OFDM encoded into exclusivetone subsets for transmission. For example, the diagram 700 shows thatbase station 1 only uses tones OFDM5:OFDM1 for transmission to its weakmobile stations. Base station 2 only uses tones OFDM 10:OFDM6 fortransmission to its weak mobiles. And base station 3 only uses tonesOFDM15:OFDM11 for transmission to its weak mobile stations. Accordingly,the mobile stations that are designated as weak by respective basestations only receive OFDM traffic on the designated tones and thusinterference by adjacent base stations is reduced. Strong traffic fromany of the base stations utilizes all available OFDM tones fortransmission.

In one embodiment in the present invention, the base stations such as BS101 shown in FIG. 1, are connected with a RNC (radio networkcontroller), the RNC is used to transfer the data with core network. TheRNC and core network are not shown in figures, but the ordinary skilledpeople will know the connection, configuration or any possible changesof the RNC structure. When the data rate control signal sent to one basestation is less than the threshold, the corresponding mobile station maycommunicate with more than one base station which all of the data ratecontrol signals sent to them is less than the threshold, that is themobile is traversing from one cell to another, or the mobile is workingin the edge in one cell. The RNC received the report signal from thebase station about the mobile status such as location and traversing,and indicate the related base stations to assign different subsets ofsub-band to the mobile device. The assigned subsets are non-overlap infrequency domain.

Furthermore, in another slot or sub-frame, the preamble may relate andassign to another mobile station, and the RNC will re-arrange the schemeof the subsets of the base station.

Those skilled in the art should appreciate that they can readily use thedisclosed conception and specific embodiments as a basis for designingor modifying other structures for carrying out the same purposes of thepresent invention, and that various changes, substitutions andalterations can be made herein without departing from the scope of theinvention as defined by the appended claims.

1. A base station wirelessly coupled to a plurality of mobile devices,comprising: a data encoder, configured to receive a preamble signal anda plurality of data streams, which are encoded into a correspondingpreamble tone and a corresponding plurality of tones, wherein thepreamble tone indicates a mapping of the plurality of tones in responseto one or more of the plurality of mobile devices, and wherein thepreamble tone indicates at least one of the plurality of tones which areaddressed to a particular mobile device, and wherein the preamble toneis not fixed to the selected particular mobile device throughcommunication; and a time division multiplexer, coupled to said dataencoder, configured to multiplex the preamble tone and the plurality oftones in timely fashion for receipt by the plurality of mobile devices.2. The base station as recited in claim 1, the base station furthercomprising a modulator coupled to the data encoder, which is configuredto sum and modulate the plurality of tones and preamble tone with aWalsh code.
 3. The base station as recited in claim 1, wherein theplurality of mobile devices receive and measure the strength of theplurality of tones and transmit a plurality of data rate control signalswhich are corresponding with the plurality of mobile devices to the basestations, the base station further comprising: a comparing unit,configured to receive and compare the plurality of data rate controlsignals with a threshold, wherein when one or more of the plurality ofdata rate control signals are less than the threshold, indicate said oneor more corresponding data rate control signals as a first traffic set,and indicate the remaining of the plurality of data rate control signalsas a second traffic set; a first traffic manager, coupled to thecomparing unit, configured to receive the first traffic set, and assigna first designated subset of the plurality of tones to the correspondingplurality of mobile devices; and a second traffic manager, coupled tothe comparing unit, configured to receive the second traffic set, andassign a second designated subset of the plurality of tones to thecorresponding mobiles devices, wherein the second designated subsetcomprises more tones than the first designate subset.
 4. A method for abase station wirelessly coupled to a plurality of mobile devices,comprising: receiving and encoding a preamble signal and a plurality ofdata streams into a corresponding preamble tone and a correspondingplurality of tones, wherein the preamble tone indicates a mapping of theplurality of tones in response to one or more of the plurality of mobiledevices, and wherein the preamble tone indicates at least one of theplurality of tones which are addressed to a particular mobile device,and wherein the preamble tone is not fixed to the selected particularmobile device through communication; and multiplexing the preamble toneand the plurality of tones in timely fashion for receipt by theplurality of mobile devices.
 5. The method as recited in claim 4, themethod further comprising summing and modulating the plurality of tonesand preamble tone with a Walsh code.
 6. The method as recited in claim4, the plurality of mobile devices receive and measure the strength ofthe plurality of tones and transmit a plurality of data rate controlsignals which are corresponding with the plurality of mobile devices,the method further comprising: receiving and comparing the plurality ofdata rate control signals with a threshold, wherein when one or more ofthe plurality of data rate control signals are less than the threshold,indicating said one or more corresponding data rate control signals as afirst traffic set, and indicating the remaining of the plurality of datarate control signals as a second traffic set; according to the firsttraffic set, assigning a first designated subset of the plurality oftones to the corresponding plurality of mobile devices; and according tothe second traffic set, assigning a second designated subset of theplurality of tones to the corresponding mobiles devices, wherein thesecond designated subset comprises more tones than the first designatesubset.
 7. A mobile device wirelessly coupled to a plurality of basestations, comprising: a decoder, configured to demultiplex and decode aplurality of tones received from at least one of the plurality of basestations; a preamble decoder, configured to decode a preamble tonereceived from at least one of the plurality of base stations, whereinthe decoded preamble tone indicates one or more of the plurality oftones are transmitted for the mobile device, and wherein the preambletone is not fixed to the mobile device through communication; and aprocessor, coupled to said decoder and said preamble decoder, configuredto process one or more of the plurality of tones indicated by thedecoded preamble tone, and send a data rate control signal of thecorresponding base station.
 8. The mobile device as recited in claim 7,wherein the data rate control signal indicates a maximum data sustainedby the mobile device according to any combination of the featuresselected form the group comprising: acceptable data error rate; channelcapacity; and loss rate of radio link.
 9. The mobile device as recitedin claim 7, wherein the mobile device is assigned with a plurality ofdesignated subsets by the plurality of base stations, the correspondingdesignated subsets are non-overlap in the frequency domain.
 10. A methodfor a mobile device wirelessly coupled to a plurality of base stations,comprising: demultiplexing and decoding a plurality of tones receivedfrom one of the plurality of base stations; decoding a preamble tonereceived from one of the plurality of base stations, wherein the decodedpreamble tone indicates one or more of the plurality of tones aretransmitted for the mobile device, and wherein the preamble tone is notfixed to the mobile device through communication; processing one or moreof the plurality of tones indicated by the decoded preamble tone; andsending a data rate control signal of the corresponding base station.11. The method as recited in claim 10, wherein the data rate controlsignal indicates a maximum data sustained by the mobile device accordingto any combination of the features selected form the group comprising:acceptable data error rate; channel capacity; and loss rate of radiolink.
 12. The method as recited in claim 10, wherein the mobile deviceis assigned with a plurality of designated subsets by the plurality ofbase stations, the corresponding designated subsets are non-overlap inthe frequency domain.
 13. A system, comprising: a plurality of basestations, each of the plurality of base stations further comprising: adata encoder, configured to receive a preamble signal and a plurality ofdata streams, which are encoded into a corresponding preamble tone and acorresponding plurality of tones, wherein the preamble tone indicates amapping of the plurality of tones in response to one or more of theplurality of mobile devices, and wherein the preamble tone indicates atleast one of the plurality of tones which are addressed to a particularmobile device, and wherein the preamble tone is not fixed to theselected particular mobile device through communication; and a timedivision multiplexer, coupled to said data encoder, configured tomultiplex the preamble tone and the plurality of tones in timely fashionfor receipt by the plurality of mobile devices; and a plurality ofmobile devices, wirelessly couple to one or more of the plurality ofbase stations, each of the plurality of mobile devices furthercomprising: a decoder, configured to demultiplex and decode theplurality of tones received from at least one of the plurality of basestations; a preamble decoder, configured to decode the preamble tonereceived from at least one of the plurality of base stations, whereinthe decoded preamble tone indicates one or more of the plurality oftones are transmitted for the mobile device; and a processor, coupled tosaid decoder and said preamble decoder, configured to process one ormore of the plurality of tones indicated by the decoded preamble tone,and send a data rate control signal of the corresponding base station.14. The system as recited in claim 13, further comprising a radionetwork controller coupled to the plurality of base stations, whereinwhen the mobile station is assigned by one or more of the plurality ofbase stations, and if the data rate control signals transmitted to thecorresponding one or more of the plurality of base stations indicatesless than a threshold, the radio network controller indicates the one ormore of the plurality of base stations to assign a plurality ofexclusive subsets of tones to the mobile device.
 15. The system asrecited in claim 13, wherein the data rate control signal indicates amaximum data sustained by the mobile device according to any combinationof the features selected form the group comprising: acceptable dataerror rate; channel capacity; and loss rate of radio link.